C5-Chemical Changes
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What are acids
Acids produce hydrogen ions (H*) in aqueous solutions. They have a pH range of 0-6.
What are alkali
Alkalis produce hydroxide ions (OH*) in aqueous solutions. They have a pH range of 8-14.
What is crystallisation
A separation technique used to produce solid crystals from a solution by evaporating the solvent.
What is a displacement
A chemical reaction in which a more reactive element displaces a less reactive element from its compound.
What is filtration
A separation technique used to separate solids from liquids
What is nuetralisation
The reaction when a acid and a base react ro form water and a salt
What is oxidation
A reaction involving the gain of oxygen.Oxidation is the loss of electrons
What is the pH scale
The pH scale, from 0 to 14, is a measure of the acidity or alkalinity of a solution, and can be measured using universal indicator or a pH probe.
What is a redox reaction
A reaction in which both oxidation and reduction occur simultaneously
What is reduction
A reaction involving the loss of oxygen. Reduction is the gain of electrons.
What is reduction with carbon
Metals less reactive than carbon can be extracted from their oxides by reduction with carbon.
What is a strong acid
A strong acid is completely ionised in aqueous solution. Examples of strong acids are hydrochloric, nitric and sulfuric acids.
What is a titration
A technique used where a solution of known concentration is used to determine the concentration of an unknown solution.
What is a universal indicator
A mixture of dyes that changes colour gradually over a range of pH and is used in testing for acids and alkalis.
What is a weak acis
A weak acid is only partially ionised in aqueous solution. Examples of weak acids are ethanoic, citric and carbonic acids.
Two reasons why a probe may be more reliable then using a indicator
More accurate results,determining the colour of the indicator is subjective
When a acids concentration is increased what happens to its pH
Its decreases. For example if it went from ph 6 to ph5 you times by 10 the concentration
Acid+metal oxide
Salt+water
Acid + metal hydroxide
Salt + water
Acid + metal carbonate
Salt +water+carbon dioxide
Why do we find pure gold in the ground, but not pure iron?
Gold is unreactive, so doesn’t react with any other elements Iron is reactive enough to react with oxygen so is oxidised to iron oxide
Reaction of lithium with water
Fizzes/bubbles (hydrogen gas produced) - Floats and moves around the surface
Reaction of sodium with water
Fizzes / bubbles more vigorously - Floats and moves around more - Makes a ball shape
Reaction of pottasium with water
Fizzes vigorously & ignites to produce a lilac flame - Floats and moves around